ADAR1 (Adenosine Deaminase Acting on RNA -1) is an essential protein required for cell survival and embryonic development. Knockout of the gene encoding for this protein in mice gives rise to rapid and wide-spread cell death resulting in embryo death. The critical role of ADAR1 in cell survival indicates a potent role for ADAR1 in regulation of the balance between cell survival and cell death under physiologic conditions, and suggests that dysregulation of ADAR1 could lead to pathology. The long-term goal of the research of ADAR1 is to define its function and mechanism in order to therapeutically target ADAR1 in pathologic processes. Our preliminary data has shown that ADAR1 directly interacts with the NF-kB pathway and up-regulates NF-kB activities through IKK protein complex in mammalian cells. The objective in this application is to identify the mechanism of ADAR1 in the regulation of NF-kB signaling. The central hypothesis is that ADAR1 modulates NF-kB mediated gene expression through a protein-protein interaction that contributes to regulation of the balance between cell death and cell survival. Two specific aims will be addressed. Aim #1: Identify the mechanism in NF-kB pathway by which ADAR1 regulates NF-kB target gene expression. The dynamic interaction of ADAR1 and IKK2 subunit upon cytokine stimulation will be defined. The biochemical and signaling consequence of the protein- protein interaction will be determined. Aim #2: Determine the functional domain in ADAR1 that binds to IKK2 and regulates NF-kB activities. The protein binding domain of ADAR1 will be determined through expressions of mutated and truncated ADAR1 in mammalian cells and detect their capabilities to bind IKK2 and regulate NF-kB target gene transcriptions. The positively or negatively functioning protein fragments will also be tested whether they rescue the cell death phenotype of ADAR1 deficiency. At the completion of these studies, it is expected that a new function of ADAR1 in NF-kB pathway and the related mechanism will be revealed. A functional domain in ADAR1 interacts with NF-kB signal pathway will be identified. This protein domain may lead to a discovery of a peptide which will be used to treat diseases due to unbalance NF-kB signaling and cell death. This study is expected to have an important impact in the fields of RNA editing, signal transduction, and diseases that involve cell death mechanisms and therefore contribute to improve human health. PUBLIC HEALTH RELEVANCE: This research has relevance to diseases related to NFkB signaling pathway, such as inflammation, arthritis, infectious and malignant diseases.